1. Field of the Invention
The present invention relates to a built-up playing court structure, enabling a selected moisture content to be maintained within its surface layer, and a method for its construction.
2. Description of the Related Art Includinq Information Disclosed Under 37 C.F.R. 1.97-1.99
There are at present two basic types of surfaces used for playing courts, "hard" surfaces and "soft" surfaces. Hard surface courts generally have concrete and asphalt surfaces and, indoors, wood surfaces. Soft surface courts generally have lawn, clay and various composite built up surfaces. To effectively play court games, one is required to repeatedly turn and move with rapidity. One of the primary disadvantages of the use of hard surface courts is that the bones, muscles and connective tissues of players are stressed by repetitive activity on the hard surface. Conventional soft surface courts however, also have disadvantages. Construction and maintenance costs are typically very high. Frequent cutting, rolling, smoothing and replenishing of the surface materials is required to keep the surface in a playable condition. Additionally, since most of these soft surface courts are constructed outdoors, and are porous, water retention following ambient rainfall may preclude play on the court surface due to puddles or a general muddy court surface having a slippery consistency.
Built-up playing courts consisting of gravel, sand, clay and various bonding materials have been developed in the art as a more practical alternative to conventional clay courts. A clay or sand top surface layer is desirable, because such a layer makes a surface more playable by providing smoothness yet appropriate traction for the soles of players, shoes. However, there are several problems inherent in such conventional built-up surfaces. Loose sand or clay which is normally present at the uppermost surface layer over time, washes down through the lower layer materials, such as gravel, due to rain or sprinkling; this sand or clay is thus lost from the surface and has to be periodically replaced. Drainage of such courts presents a problem because the sand or clay tends to fill all of the void spaces between the lower surface materials (e.g. gravel). Thus, water will not drain laterally below the surface at a sufficiently fast rate. Hence, water drainage usually runs off over the top surface, gradually removing the surface materials. Even if the surface materials are not washed away, they tend to be redistributed unevenly, causing smoothing problems. Furthermore, unless the surface is adequately sloped and almost perfectly uniform, there will be standing puddles of water following rains which will preclude use of the court until the water is removed by evaporation. Almost all conventional soft surface and hard surface courts have a slope in an attempt to prevent puddling. Another problem occurs in cold weather areas. Water trapped within the void spaces below the surface freezes. The expansion that takes place during freezing causes movement of the surface, thereby damaging it. Repair is necessary to smooth the damaged areas. Another problem is that wind tends to blow away or unevenly rearrange surface materials, especially when the surface is dry; again, requiring replacement or smoothing. This problem could be alleviated considerably by sprinkling the surface with water. However, during periods of winds or play, sprinkling is impractical. Another problem with wind is that the top surface tends to dry out, resulting in poor footing for the players and inconsistent ball bounce.
Since court games, particularly tennis, are played by millions of people, much time and energy has been devoted to solving such problems inherent in maintaining outdoor athletic courts or similar structures. Examples of proposed solutions to some of the problems are disclosed in U.S. Pat. Nos. 585,856, entitled Underground Irrigation, to Swanson; U.S. Pat. No. 3,307,360, entitled Method of Subsurface Irrigation and System Therefor, to Bailly; U.S. Pat. No. 3,625,010, entitled System and Method for Preventing Erosion, to Hakundy; U.S. Pat. No. 1,222,648, entitled Growing Trough, to Marks; U.S. Pat. No. 2,031,146, entitled Automatic Watering Device, to Dodge; Czechoslovakian Patent No. 111978 to Sramek; Italian Patent No. 482615 to Ortensi; German Patent No. 27 27 956, to Blank; U.S. Pat. No. 1,862,423, entitled Playing Court, to Otto; U.S. Pat. No. 1,958,850, entitled Tennis Court, to Foster; U.S. Pat. No. 4,015,432, entitled Stabilizing Subsoil Moisture Under Light Structures, to Ball; U.S. Pat. No. 1,690,020, entitled Pavement and Process of Laying Same, to Kirschbraun; U.S. Pat. No. 2,024,158, entitled Playing Court, to Gallagher; U.S. Pat. No. 4,044,179, entitled Playing Surface for Athletic Games, to Haas, Jr.; U.S. Pat. No. 3,908,385, entitled Planted Surface Conditioning System, to Daniel, et al.; and U.S. Pat. No. 4,576,511, entitled Apparatus and Method of Creating and Controlling an Artificial Water Table, to Vidal, Jr. None of these patents teach the unique court surface structure of the present invention having a built-up court surface layer, a stabilizing subsurface layer, and means for selectively controlling moisture content in the built-up court surface layer. These patents are discussed in more detail below.
The '856, '360, '010, '648, '146, patents and Czechoslovakian Patent No. 111978, disclose subsurface irrigation devices. The irrigation systems are used for providing water to a vegetative or natural soil surface cover. Italian Patent No. 482615 and German Patent No. 27 27 956 disclose a subsurface irrigation system for sports fields with granular surface covers. The '432 patent discloses a subsurface moisture barrier.
The '020, '158 and '179 patents disclose permanent, fixed surfaces. The '020 patent is directed to a combined bituminous and concrete pavement surface. The '158 patent teaches a playing court surface atop cork/sand gravel beds. The '179 patent discloses an artificial turf fabric surface which is intended to simulate grass.
The '385 patent discloses a system for irrigating and evacuating a playing field having a vegetative cover. This system incorporates a lattice of perforated pipes under the playing surface. The pipes are covered by a layer of sand followed by a layer of rooting media on which the vegetative matter is grown. A pump attached to the pipe lattice allows a vacuum to be applied and accumulated surface water to be drawn down within the subsurface sand layer. Also incorporated into the system is a moisture sensor which allows automatic irrigation of the field.
The '423 patent discloses a soft surface court having a pervious surface layer which enhances drainage and moisture retention, depending upon ambient conditions. The '850 patent teaches the use of fine epidote as a top layer and coarser epidote as a lower layer for a tennis court surface. Neither of these patents provide means for moisturizing the surface.
The '511 patent discloses means and apparatus for maintaining a selected water level in a layered structure of particulate material.